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MILES O'BRIEN, CNN ANCHOR: Right now, we're going to have to listen to some folks from the United States Department of Agriculture, Dr. Ron DeHaven, Dr. Ken Peterson, Dr. Steve Sunloft (ph) there, to brief reporters in Washington, give us the latest on the mad cow concerns that we all have, try to shed some light on the source of it, and thus give us a sense what the risks might be. I believe we're going to hear from Dr. DeHaven first. Let's listen. RON DEHAVEN, CHIEF VETERINARIAN: Thank you. We appreciate you all being here and for your continued interest and accurate reporting on this very important issue.

Let me speak first from the investigation standpoint. We are continuing to work with our Canadian colleagues to verify the trace- back of the index or positive animal.

One issue that has been of particular concern was the initial discrepancy in the age of the animal, as reported by our records in the U.S., versus those records that were available in Canada.

Yesterday, I personally telephoned the owner of this herd where the positive animal was located, primarily to thank him for his cooperation, thus far, in this effort. However, during that discussion, he indicated that he has conducted an extensive search of his records and located original documents that would indicate that the cow in question -- this positive animal -- was, indeed, an older animal when he purchased her in 2001.

Those records are consistent with the Canadian records indicating that this animal was born in April of 1997, making her approximately 6.5 years old at the time of slaughter.

So, again, I want to personally thank him and his employees for the extraordinary level of cooperation that they have shown to our investigators throughout what is, no doubt, a very difficult time for them.

The age of the animal is especially important in that it is a likely explanation as to how this animal would have become infected. She would have been born before feed bans were implemented in North America, as the feed bans in the U.S. and Canada both went into effect in August of 1997, And as I mentioned, records would now indicate that this cow was born in April of 1997.

Again, those feed bans prohibit the inclusion of ruminant protein, that would be material from animals such as cattle, sheep and goats, from being fed back to other ruminants. Research evidence suggests that this is the primary, if not the only means, by which BSE is spread from animal to animal.

Obviously, the more time goes by, the fewer animals that are alive that have been exposed to feed before this feed ban went into place. And so as time goes by, the risk of more animals becoming infected decreases.

Even though we have now resolved or apparently resolved the earlier discrepancy regarding the actual age of this animal, only DNA testing will positively confirm her origin.

Again, our primary line of inquiry goes to a farm in Alberta, Canada, and our Canadian counterparts are working hand in hand with us, sharing information, records and samples that will enable us to perform this DNA testing to hopefully confirm the actual herd of origin for this particular animal.

We are continuing the trace-back of the other 73 head of cattle that came into the United States in the same shipment as the infected cow, but do not have any new data to report in that regard at this point.

However, while reviewing records, we have also determined that an additional eight animals from the same herd in Canada were shipped to the United States. So we are now tracing the location of all 81 animals.

As I mentioned previously in previous press conferences, this positive cow had three calves while she was in the United States. One of them died shortly after birth, shortly after the animal entered the United States. The second one remains in a herd in Washington state where the positive cow was at the time that she went to slaughter.

And the third animal, a bull calf, is currently in a separate herd with several other bull calves, which is subject to a hold order in place by the state of Washington. And as I explained before, as well, this hold order is not to stop the spread of the disease. BSE is not a contagious disease like we would associate with conditions such as human flu, but rather the hold order has been put in place to make sure we know where all of the relevant animals are with regard to this investigation and to prevent future complications as it relates to the investigation.

I would emphasize, again, even though we are following up on these three calves, that maternal transmission -- transmission from the cow to her offspring -- is a rare means of transmission if it occurs at all. Therefore, it would be highly unlikely that this type of transmission would occur in this case.

However, as I mentioned, the calves that are still alive -- there's two, one on the index farm, and the other in this calf-rearing facility -- are on hold orders out of an abundance of caution to preserve public and international confidence that we, in fact, have the situation well in hand with regard to our investigation. We are continuing to look at any and all appropriate changes to our entire meat and livestock system as it relates to BSE. Even though we are still early in this investigation, there is no indication that we have the magnitude of problem that Europe has experienced in the years past, in large part due to the preventive measures such as feed bans that were put in place in this country back in August of 1997.

There is also no reason to question the safety of the U.S. beef supply. Muscle tissue, or cuts of meat, are safe. Research shows that the prion, which is that infectious agent that causes BSE, is not found in skeletal muscle tissue. The infective agent is largely in the brain and spinal cord and a few other tissues not normally consumed by humans in this country.

Research studies, in which muscle tissue from infected cattle has been injected directly into the brain of other cattle, the most likely way to transmit the disease when infectivity is present, have demonstrated no evidence of transmission of the disease through muscle tissue.

In contrast, high-risk tissue, such as brain or spinal cord, in the same study do cause the disease when they are either fed to or injected into recipient cattle.

Current international standards allow for the import of meat and other commodities, even from countries that have a high or moderate risk for BSE, those countries that have had numerous cases of BSE in their own native-born cattle.

These international standards have been developed with the advice and consult of many of the top international scientists and researchers in the field of BSE.

By any stretch of the imagination, the U.S. cannot be considered to be at high risk for BSE, especially given our high level of surveillance over the recent past and the fact that only one case of the disease has been found here; and further, that a single case appears not to have been even born in the United States at this point.

International reaction to our find of this positive case has been based largely on public perception and not what we know about the science of this disease. We have been working with the world animal health organization, the OIE, especially since the finding of the single case of BSE in Canada in May of this year, to ensure that the international response to a case of BSE is better founded in science and not just in public perception.

Even with the finding of this single cow, the U.S. remains at very low risk. Measures we put in place in this country years ago, including the prohibiting of feeding rendered cattle products back to other cattle and stopping cattle imports from high-risk countries, are protecting the U.S. consumer.

Further, we have conducted surveillance testing of high-risk cattle for more than 10 years, and this is our only positive find, despite that high level of surveillance testing.

For the last two years, we conducted approximately 20,000 tests each of those two years, more than 45 times what the world animal health standard would call upon us to test.

An extensive risk assessment was conducted by Harvard University, and that assessment demonstrated that the risk of BSE in the United States is very low and that even with the disease, our procedures that we have put in place would be eliminating the disease from our population.

The producer recalled the meat and the recall in this situation from this cow and others slaughtered on that day has been done out of an abundance of caution. The risky materials, especially the central nervous system, the brain and spinal cord from this animal, were removed and they went into rendered product for inedible purposes and did not go into the human food chain.

Again, I want to reiterate my thanks to the herd owner, the slaughter plant owner, the importers, the officials in the state of Washington and our colleagues in Canada for their tremendous assistance as we have proceeded with our investigation.

And, again, my thanks to you in the news media who have been working so hard to ensure that the reporting on this situation is accurate and is timely in recognizing that this situation is evolving very rapidly.

O'BRIEN: With that, we're going to leave that news conference. We, of course, will be monitoring it. We've been listening to Dr. Ron DeHaven, USDA's chief Veterinary Animal Plant Health Inspection Service, head of that division.

One of the key things is he mentioned in talking to the owner of the herd where the suspected cow exists, is that in further culling his records there, the owner of that herd believes that the infected cow might have been an older cow, just to say 6 1/2 years old. That's a critical point, which leads to the level of concern we should all have.

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